Plasma-generating devices relate to devices which are arranged to generate a gas plasma. Such devices can be used, for instance, in surgery to stop bleeding, that is coagulation of biological tissues.
As a rule, said plasma-generating device is long and narrow. A gas plasma is suitably discharged at one end of the device and its temperature may cause coagulation of a tissue which is affected by the gas plasma.
Owing to recent developments in surgical technology, that referred to as laparoscopic (keyhole) surgery is being used more often. This implies, inter alia, a greater need for devices with small dimensions to allow accessibility without extensive surgery in surgical applications. Equipment with small dimensions are also advantageous to allow good accuracy in the handling of surgical instruments in surgery.
WO 2004/030551 (Suslov) discloses a plasma surgical device according to prior art which is intended, inter alia, to reduce bleeding in living tissue by a gas plasma. This device comprises a plasma-generating system with an anode, a cathode and a gas supply channel for supplying gas to the plasma-generating system. Moreover the plasma-generating system comprises at least one electrode which is arranged between said cathode and anode. A housing of an electrically conductive material which is connected to the anode encloses the plasma-generating system and forms the gas supply channel.
It is also desirable to provide a plasma-generating device as described above which is capable, not only of coagulation of bleeding in living tissue, but also of cutting tissue.
With the device according to WO 2004/030551, a relatively high gas flow speed of a plasma-generating gas is generally required to generate a plasma for cutting. To generate a plasma with a suitable temperature at such gas flow speeds, it is often necessary to supply a relatively high electric operating current to the device.
It is nowadays desirable to operate plasma-generating devices at low electric operating currents, since high electric operating currents are often difficult to provide in certain environments, such as medical environments. As a rule, high electric operating currents also result in extensive wiring which can get unwieldy to handle in precision work, for instance in keyhole surgery.
Alternatively, the device according to WO 2004/030551 can be formed with a substantially long plasma channel to generate a plasma with a suitable temperature at the required gas flow speeds. However, a long plasma channel can make the plasma-generating device large and unwieldy to handle in certain applications, for example medical applications, especially keyhole surgical applications.
The plasma generated should in many fields of application also be pure and have a low degree of impurities. It is also desirable that the generated plasma discharged from the plasma-generating device has a pressure and a gas volume flow that are not detrimental to, for instance, a patient who is being treated.
According to that described above, there is thus a need for improved plasma-generating devices which can be used, for instance, to cut biological tissue. There is thus a need for improved plasma-generating devices which can generate a pure plasma at lower operating currents and at lower gas volume flows.